"""
题目：两个变量值互换。
"""
def exchange(a,b):
    a,b = b,a
    return (a,b)

if __name__ == '__main__':
    x = 10
    y = 20
    print("x = %d,y = %d" % (x,y))
    x,y = exchange(x,y)
    print("x = %d ,y = %d " %(x,y))